I play on my desktop most often because the GFX card kicks ass (imo). Too bad the processor sucks:
Upgraded HP m7780n
Intel Core 2 Duo E6400 @ 2.13 Ghz
4 GB DDR2 Memory @ 667 Mhz
ATi Radeon HD 5850 1 GB DDR5
2x Western Digital 25 0GB SataII (don't know the model)
My laptop has a much better Gmod experience because of the processor, but newer games don't like the graphics chip:
Stock HP dv7-3085dx
Intel Core i7 720QM @ 1.6 Ghz ( turbo boost raises it to 2.8 sometimes >:-) )
6 GB DDR3 Memory @ 1066 Mhz
NVidia GeForce GT 230M 1 GB
Seagate 500 GB SataII (again, don't know the model)